How bioenergy works

Plants use photosynthesis to capture the sun’s energy, and this energy is stored as they grow providing a source of bioenergy. Bioenergy comes from trees and crops grown for their energy content and from by-products such as sewage, straw, manure, animal and vegetable fat and rubbish. These energy sources are referred to as biomass feedstocks.

Biomass can be burned to produce heat. This heat can be used directly or used to generate electricity. Biomass can also be turned into biofuels that act as substitutes for fossil fuels in transport.

Biofuels

The most common types of biofuels are biodiesel (an alternative to diesel) and bioethanol (an alternative to petrol). Biodiesel is made from vegetable oils or animal fats - a biodiesel blend is biodiesel blended with ordinary diesel. Bioethanol is alcohol fuel made from waste, by-products and plants that contain sugars and starches. It’s usually available as a blend, mixed with petrol.

As a driver, you can reduce the impact of climate change by using biofuels, which result in fewer greenhouse gas emissions than fossil fuels.

Pros and cons of bioenergy

Using bioenergy will have almost no greenhouse effect as long as the carbon dioxide given off during its use is absorbed by the next crop of biomass. Beyond greenhouse gas emissions, the total environmental impact of a bioenergy source depends on how the feedstock is produced.

It can be cheap if the biofuel you use is a by-product of something already being made on the same site. However, costs of using bioenergy can outweigh benefits - for example, if you have to gather fuel from too wide an area or if transporting it is expensive.

The future of bioenergy

Recent innovations are making it cheaper and easier to make biofuels. Advanced (or second generation) biofuels made from sustainable feedstocks such as wood, straw and waste are being developed here and overseas. Bioethanol and synthetic petrol and diesel can be made from wood residue, but the processes have yet to be successfully commercialised.

Research by forestry Crown Research Institute, Scion, shows bioenergy from different sources could supply a significant amount of New Zealand’s liquid fuel and heating demands.